1. Field of the Invention
The present invention relates to a recording and reproducing apparatus for an optical recording medium such as a recording optical disk and a laser-driving pulse adjusting method and, in particular, to a technology that properly perform the adjustment of a laser-driving pulse (write-strategy) in accordance with an apparatus and/or recording medium therefor.
2. Description of the Related Art
Examples of related art include JP-A-2005-149580 (Patent Document 1), JP-A-2005-222634 (Patent Document 2) and JP-A-2004-185796 (Patent Document 3).
It has been known that an optical disk recording technology includes the adjustment of a laser-driving pulse for writing such as the so-called write-strategy.
First of all, the terms, “write edge position”, “mark edge position” and “mark edge position error” will be described as terms used in describing the write-strategy in a technology in the past and a technology according to the invention.
FIGS. 15A, 15B and 15C show examples of a data bit array, write waveform and read waveform. The data bit array in FIG. 15A has serial sections of 3T marks, 2T spaces and 2T marks where T is a channel clock length. The write waveform in FIG. 15B includes pulses driven by a laser diode of an optical head (optical pickup), which are generated as pulses in accordance with the mark length to be written. The read waveform in FIG. 15C is a read RF signal waveform obtained when information recorded on an optical disk is read by the laser-driving pulse in FIG. 15B. The broken lines indicate timings of read clocks generated by a PLL. Data is sampled in timings indicated by circles, which are read clock timings, from a read waveform. For example, binarizing and decoding processing may be performed thereon with reference to the slice level, for example.
The term, “write edge position”, herein refers to the edge position to be used for adjustment by the write-strategy on a write waveform and may be the edge position of the part indicated by the arrow RE in FIG. 15B.
The term, “mark edge position”, herein refers to an error caused between the position of the crossing point between a read waveform and a slice level and the middle position of a read clock timing. For example, the mark edge position may be the position indicated by the arrow MEP in FIG. 15C, which is the crossing point between a read waveform and a slice level. In the case in FIGS. 15A to 15D, the position indicated by the arrow MEP is the mark edge position upon transition from 3T marks to 2T spaces. FIG. 15D is an enlarged view of the part near the mark edge position MEP in FIG. 15C. Originally, a read waveform desirably crosses with the slice level for binarizing processing at the middle timing of a read clock timing. The mark edge position here is the displacement indicated by the arrow MEP between the middle timing indicated by the dot-dash line in FIG. 15D and the crossing point between the read waveform and the slice level.
The term, “mark edge position error”, refers to a subject value to be adjusted to zero, which may be the mark edge position itself. Alternatively, the mark edge position error may be a difference from the reference, which is the mark edge position of one mark length here.
The mark edge position may be used as the subject value for the strategy adjustment for a laser-driving pulse. The mark edge position error is the value indicating a time error between the crossing point between a read waveform and a slice level and a read clock timing. The strategy is adjusted to have a uniform mark edge position error for all mark lengths.
In order to perform adjustment with a mark edge position as the strategy adjustment on a laser-driving pulse in the past, the mark edge position error is detected, and the write waveform is moved by the amount of error to adjust (as disclosed in Patent Document 3).
For example, a case will be described in which the mark edge position at the rear end of the 3T marks is displaced from another mark edge position in the plus direction (on the right side in FIGS. 15A to 15D) by 1 [ns] as shown in FIGS. 15A to 15D. In this case, the trailing edge position RE of the write waveform of the 3T marks is corrected to the left side by 1 [ns] as indicated by the arrows wx and wy, whereby the mark edge position at the rear edge of the 3T marks is justified.
The write edge position corresponding to the mark edge position error detected in this way is moved and adjusted by the amount of error.